Illumination devices comprising a light source and a reflector system forming a spotlight and one or several actuators arranged to pivot the spotlight in a mounting base for varying an illumination angle of the light beam emitted by the spotlight are known as moving head lamps or as robotic lamps. Robotic lamps comprise rather small actuation motors which are in contrast to the motors in moving head lamps lower in cost and much slower in actuation. Therefore, robotic lamps can be installed in a high number and allow aiming of the emitted light beam without the need for climbing a ladder for the light designer. The actuation motors are simply connected through wire or wirelessly to a control station at which the light designer can control the pivoting of the spotlights.
U.S. Pat. No. 6,079,862 A describes an automatic tracking lighting equipment for automatically tracking a target to be illuminated. The spotlight is supported for pivoting in horizontal and vertical directions on a ceiling surface. A horizontal drive mechanism changes the horizontal angle of the spotlight and a vertical drive mechanism changes the vertical angle of the spotlight. A CCD camera is attached to the housing of the spotlight and picks up the image of a target area to be illuminated. The target to be illuminated is recognized by an image recognition unit which processes the image from the CCD camera. According to the calculated coordinates of the target, the driving mechanisms are automatically driven to pivot the spotlight in a desired direction.
Such an illumination device is applicable without severe problems in applications in which the size of the spotlight and the generated lighting effect are small compared to the distance between the spotlight and the target surface. This is mostly the case in theaters, on stages or in studio lighting. This is not the case in the field of display lighting for stores in which the target regions are closer to the spotlight. In these applications, parallax errors between the spotlight and the camera axis reduce the accuracy of the aiming. Positioning the camera on the optical axis of the spotlight on the other hand produces undesired shadows in the illuminated target region.